List of abbreviations. 2
Aims and Objectives. 5
Discussions and Conclusion. 8
List of abbreviations
KEBS: Kenya Bureau of Standards
ASTM: American Society for Testing and Materials
OPEC: Organization of the Petroleum Exporting Countries
Mb/d: Million barrel per day
ASAL: Arid and Semi-Arid Land
NDMA: National Drought Management Authority
NETFUND: National Environment Trust Fund
MT: Million tonnes
Various studies conducted in the recent past on the exploration of biofuels as a renewable energy source has been triggered by the increasingly adverse effects of climate change experienced and reduction of fossil fuel reserves. Most of the fruit waste released during the fruit processing can be reused to produce ethanol which will help immensely in curbing pollution and help in waste management. In the future, this will have a positive spiral effect to the environment. This study’s objective is to examine the availability and efficiency of the usage of the mango waste, Mangifera indica L. to produce bioethanol through fermentation by yeast, Saccharomyces cerevisiae. Both the local and exotic varieties will be examined. The study is to be carried out through field samples and laboratory tests on the samples taken. The results obtained from the laboratory tests are to be compared to, first, the established bioethanol quality criteria by KEBS specifications (KEBS, 2010)and any other standards relevant in Kenya. Secondly, trace element levels, physical constants, and other chemical properties are to be compared to ASTM standard specifications. The levels are expected to be on permissible ranges. Increased bioethanol production is expected to be directly proportional to the increased fermentation time. Greenhouse gas emissions are anticipated to lower with expanded bioethanol percent in the blended fuel.
With the rapid extraction of fossil fuels to generate petroleum products such as petrol and diesel to foster ever-increasing demand in the transportation, petrochemical and other economic sectors, a permanent solution to an alternative fuel that will compete efficiently is urgently required. According to OPEC, long-term oil demand is set to increase from 15.8 mbd (2016) to 111.1 mb/d in 2040, significantly in the developing countries (OPEC, 2017), which translates to massive degradation of the environment through oil spills and increased greenhouse gas footprint, especially methane. Thus, alternative fuels that are environmentally friendly and cost-effective, are the viable option for most developing countries looking into stronger economic growth in the future. Kenya is already making strides in producing bioethanol and biodiesel as biofuels. Bioethanol is primarily produced in Kenya from feedstock crops such as cassava, sugarcane, and sweet sorghum. Currently, the aforementioned feedstocks require more than 400 millimetres of rainfall annually, which locks out ASAL from producing them abundantly. Kitui County is one of the regions identified as an ASAL by the NDMA, though one of the leading counties in mango production in Kenya. According to NETFUND, Kitui County produces almost 61% of the mangoes in the Eastern region of Kenya. Around a million tons of seeds and peels are disposed of by the fruit processing industries, for which the research has shown that they can be converted into bioethanol (Saifuddin, et al., 2014). Mango peels and seeds are the most useful in the mango waste because they possess valuable traits that make them potential feedstocks. They contain high cellulosic and hemicellulosic load that can be hydrolyzed into fermentable sugars (Carla-da, S. M., et al., 2010).
According to NDMA, Kitui County risks facing severe drought due to the poor vegetation condition index, which classifies it as an ASAL (NDMA, 2017). This puts pressure on the county government to provide ways to enhance drylands agriculture and value addition in the post-harvest and processing of fruits and crops. Mango has been identified as such to be adaptable to the semi-arid climate in Kitui County. The local varieties grown are Ngowe, Dodo, and Boribo, whereas the exotic varieties are Apple, Kent, and Tommy (Mulinge, 2015). On a country level, the production is set to peak to 1,415,000 MT in 2022, 61% increase from 2017 (Owuor, 2015). This translates to increased availability of bioethanol feedstocks through waste. Efforts have been made by various local fruit processors to reduce post-harvest losses and augment heterogeneity in the consumption of the mango since the fruit is produced seasonally. The efforts include processing of the fruit into juice, powder or fortified flour. The mango fruit processors in Kitui County are Rise Kenya Migwani, Mwingi Horticultural Cooperative Society, Mwingi Fruit Processors, Mukyie Mumoni and Kyuso organizations, Chuluni Horticultural, Kitui Development Centre and Kitui County fruit processing cooperative society. Currently, the post-harvesting losses are set at 40% (Owuor, 2015), which indicates that both rotten waste from the farms and processed waste in the factories will be utilized in bio-ethanol production. Thus, forms the need to ascertain the availability and efficiency of mango waste to produce bio-ethanol in Kitui County, Kenya.
Aims and Objectives
1. To ascertain the availability of the mango waste to produce bioethanol.
2. To determine the quality of the bioethanol fuel produced from the mango waste against alternative fuel standards.
3. To determine the efficiency of bioethanol in combination with the gasoline as a blended fuel.
The methodology tries to justify the hypothesis: There is an adequate supply of mango waste in Kitui County that can produce bioethanol efficiently, and the research questions:
1. Does Kitui County have an adequate supply of mango waste?
2. Is the mango waste obtaining the right type to produce bioethanol?
1.1 Collection of the mango waste and removal of the unwanted foreign matter:
Rotten mango waste, Mangifera indica L. is to be gathered from preferred farm sites, based on different agro-ecological zones suitable for farming in Kitui. They include Migwani, Kitui Central, Mutongoni, Matinyani, Changwithya, Nzambani, and Miambani. In addition, the mango waste will be collected from the mango processors situated in Kitui County. The mango waste will be stratified and sampled according to the type of mango, that is either indigenous or exotic. The mango waste will be washed using quaternary ammonium compounds such as potassium permanganate (KMnO4) after removal and sorting of unwanted foreign matter such as stone pebbles and sand particles. Then the mango waste will be rinsed in warm, distilled water.
1.2 Preparation of the sample and measurements:
The rotten mango waste will then be peeled using peelers, the seed to be removed using hands to be utilized in another medium such as making of food powder. The fruit pulp and peel will then be ground using a mixer to ensure homogeneity of the thick mixture. For the purpose of this study, a sample of the mixture is to be weighed to 400g and the number of samples will be dependent on the variety of the mango types. The sample is then filled into 1000 ml Schott narrow mouth reagent bottle. Total Soluble Solids (TSS) and Total Dissolved Solids (TDS) value of sample before fermentation is to determined. TSS will be obtained using two methods, that is gravimetric and spectroscopy. The former one will use the evaporating dish, filter and thermostatic oven set at 105oC, whereas the latter one will use the Fourier Transform Near-Infrared (FT-NIR) spectrometer (Ying, Liu, Wang, Fu, & Li, 2005). TDS will use the conventional oven method described in the gravimetric method. The pH value is to quantify using the pH meter.
In a beaker of 1000ml, 300ml of slightly warm distilled water is to be added together with
50gm of sucrose and 10gm of prepared Saccharomyces cerevisiae. The mixture is to be stirred well with a mechanical mixer.
This mixture is then to be poured into the 1000 ml Schott narrow mouth reagent bottle which contains the 400g of the mango waste sample. Warm distilled water is added to mark up to the final volume of 1000 ml. The mixture obtained is first to be agitated in small swirls, then shaken well to ensure uniform distribution of the yeast and the fruit sample.
The mixture is then to be placed in a rotary shaker incubator for 36 hours at a speed of 180 rpm and at a temperature of 36oC.
All parameters/control tests will be tested in triplicates.
1.4 Fermentation at differing operating conditions:
Other test experiments are to be performed similarly to the fermentation process described above. The changes will be a modification of the operating conditions, that is the temperature, pH, yeast concentration and incubation time. The temperature will be varied based on + 10oC limit, the pH will be reduced to more acidic medium, of saying to pH of 4 and for the yeast, the concentration will be increased gradually up to 40 grams. Lastly, the incubation time will be increased to increase the rate of fermentation.
1.5 Vacuum filtration:
After the fermentation process, the samples will be transferred from the incubator into the Buchner funnel, connected to a suction pump for the vacuum filtration. Then the tests (TSS, TDS, and pH) will be performed afterward.
1.6 Fermentation efficiency:
The bioethanol yield is set to be established by using dichromate colorimetric method (B. Williams & Darwin Reese, 1950), which is a direct reaction of ethanol and the dichromate ions in presence of sulphuric acid, and determination of ethanol absorbance at 575 nm wavelength using a spectrophotometer (Ethanol assay). The percentage of ethanol is to be evaluated after comparison of the absorbance values to the ethanol standard graph estimation.
Due to the complex nature of the sugars present in the sample, glucose content is to be determined using the dinitrosalicylic method (Miller, 1959) and the absorbance to be measured against the reducing sugars standard graph at 450 nm wavelength using an FT-IR (Fourier Transform Infrared) spectrometer.
1.7 Metal and metalloid content of bioethanol:
The mango waste samples, together with the yeast sample are to be analyzed to quantify the elemental content by using multielement oil analyzer (MOA II). The metals to be analyzed are lead, chromium, iron, manganese, mercury, and aluminium. The analyzed metal levels are to be within permissible levels.
1.8 Viscosity and acid value analysis:
The acid value is to be determined using sodium hydroxide titrant. For viscosity test, the samples are to be placed in a 500ml beaker and heated up at 40°C and then measured by using rotational viscometer. The viscometer torque is to be set at 30 rpm. Then the Brookfield spindle number 63 is to be used.
1.9 Microbial load analysis:
The microbial content of the produced bioethanol is to be measured to check that the bacteria and molds are not on contaminable levels. The tests will be standard plate count, total coliform count, presumptive test and yeast and mold test. Different media culture will be used in the tests.
2.0 Engine test and calorific value analysis:
Engine emission of the bioethanol to be tested by generating it using the multi-cylinder, multi-stroke spark ignition petrol engine for 1 hour at varying rotational speeds, that is 1200,1600 and 2000 rpm. The exhaust gas pollutant concentrations, which are different compositions of the hydrocarbon, carbon, nitrogen and Sulphur oxidized compounds will be tested for the various petrol blends such as E0 (100% petrol), E5 (a blend of 5% bioethanol with 95% petrol) and E10 bioethanol (a blend of 10% bioethanol with 90% petrol). The calorific value will be determined using a bomb calorimeter.
Discussions and Conclusion
The availability of mango waste, especially the indigenous type is expected to increase during the peak seasons when there is usually glut in supply of mangoes. The glucose content, total soluble solids (TSS) and pH values are set to decrease after the fermentation and inversely true to TDS, because of conversion of glucose to bioethanol. For the engine test results, levels of hydrocarbon, nitrogen, sulphur and carbon compounds will be much lower in ethanol blended fuels as compared to 100% fossil fuel petrol. Most of the metals are expected to below the critical limit set up by KEBS and ASTM.
The aim of this research proposal is to unleash the untapped potential and the resourcefulness in producing bioethanol from mango waste and also doubles up as an environmental waste management technique through recycling. Lastly, lesser carbon footprint through reduced greenhouse gas emissions.
1. The development blueprint on joint venture partnerships with the corporate sector should be administered to create market networks and educate the masses on the utilitarian potential of the mango waste as a biofuel feedstock.
2. Microwave activation of the biomass through hydrolysis in a setup bio-refinery.
3. Near-infrared reflectance spectroscopy (NIRS) analyses should replace the conventional method of ethanol determination. This is because the dichromate colorimetric method uses the destructive approach that leads to poor estimation.
4. More accurate methods of metal determination should be incorporated to replace the oil analyzer since the metal and metalloid concentrations are extremely low. Examples include Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Mass Spectrometry (ICP-MS) together with Atomic Absorption methods.
5. Laser sensor technology to be infused in the engine test. Laser Doppler velocimetry magnifying sensors can be used to accurately measure the movement of the exhaust gas particles during the combustion cycle.
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Miller, J. L. (1959). Use of dinitrosalicylic acid reagent for determination of reducing sugar. Anal Biochem 31: 426-428.
Mulinge, W. K. (2015). Factors influencing grafted mango (Mangifera indica L.) production in Matinyani division, Kitui County. South Eastern Kenya University.
NDMA. (2017, November 27). Retrieved from http://www.ndma.go.ke/index.php/resource-center/send/39-drought-updates/4661-vegetation-condition-index-as-at-november-27-2017
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